Cone for use in wireless loudspeakers, telephones, and the like



TELEPHONES AND THE LIKE Feb. 4, 1936.

F. HARRISON CONE FOR USE IN WIRELESS LOUDSPEAKERS,

A Filed Nov. 22, 1935 INVENTOR I f/yorr/soxz ATTORNEY Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE CONE FOR USE IN WIRELESS LOUDSPEAK- ERS, TELEPHONES, AND THE LIKE Frank Harrison, Braintree, England 9 Claims. (01. 181-31) This invention relates to a new and improved type of cone diaphragm for use in wireless loudspeakers. telephones, and in all instances where impulses, electrically produced or otherwise, are required to be made distinctly audible.

'I.'ne principal object of the invention is to provide an acoustic diaphragm of this type which will give a better all-round response over the frequency range and, in particular, a greatly improved or extended response in the lowest part of such range.

with this object in view, according to the invention, an acoustic diaphragm of the type set forth comprises a portion which has an apical angle of less than and an axial depth substantially greater than the diameter of, or greatest dimension across, the mouth of such portion. With a cone formed by a straight-line generatrix, the latter condition follows from the first. With a cone formed by a curved generatrix, however, it is important that the portion having an angle of less than 30 should also be of material depth, '1. e., of a depth at least twice the diametrical dimension at the mouth of such portion. Known diaphragms having a small angle at or about the apex of the cone but a large general or contour angle are accordingly relatively shallow and do not achieve the aforesaid object of the invention.

Preferably the diaphragm comprises an apical portion which is substantially a tube with a slight conical taper. At the mouth of this portion, a second conical portion with a larger angle and convenient diameter of opening may be formed or provided This second portion serves largely for amplification purposes. In the case of anapical portion formed by a curved ,generatrlx, the apical angle may be as low as 50 or .may even be zero. An exponential shape of cone may be employed, but is rather too long for practical purposes. To avoid this difliculty, the intermediate portion of the exponential shape may be dispensed with and the apical and mouth portions connected to ,form a diaphragm as hereinafter set forth.

The diaphragm according to the invention may be driven by any type of loudspeaker unit, telee phone device or the like. with the same advantage in a gramophone provided. as is necessary with this type of diaphragm, that the impulses are applied substantially axially at or about the apex of. the cone and that said diaphragm is supported or suspended so that it can vibrate freely over its whole area. The diaphragm may also be employed as a sound receiving diaphragm under analogous conditions.

It may also be employed,

Various forms of diaphragms constructed according to this invention will now be described with reference to the accompanying drawing, in which:

Figures 1, 2 and 3 are longitudinal diagrams of three forms of diaphragms constructed according to this invention;

Figure 4 is an axial diagram showing in dot and dash lines an exponential horn and in full lines the parts .of this horn which are taken to provide a diaphragm according to this invention;

Figure 5 is a diagram showing a horn similar to Figm'e 1 attached to a battle board and connected to a loudspeaker unit:

Figure 6 illustrates the shape of an ordinary coach horn which can be employed as a diaphrasm;

'7 is a sectional diagram of a diaphragm or cone fitted with means for holding a needle and suitable for reproducing sound from a gramophone record;

Figure 8 is a diagrammatic elevation of a gramophone fitted with the improved diaphragm which acts as the horn;

9 is a plan thereof;

Figure 10 is a diagram of a similar type of diaphragm to that shown in Figure 1 adapted for gramophone use and having a usual tone arm indicated by dotted lines, and

Figure 11 is a diagram showing the tubular extension disposed within the conical part of the diaphragm.

Referring more particularly to Figure 1, the diaphragm is made up of an elongated tubular portion I of considerable length in relation to its diameter. This portion I may, for example, have a diameter at its end 2 of of an inch or less and at the other end 3 the diameter may be, say, of an inch to of aninch. The length from the end 2 to the other end 3 of this tubular extension may be approximately 4 inches. To the wider end 3 of this tubular portion l is attached in any suitable manner a truncated cone 4 of any suitable angle, preferably an angle of 90, but obviously this angle may be varied according to the diameter required. Further, the length and diameters of the tubular portion may be varied to suit requirements. The truncated cone 4 may be secured to the end 3 of the elongated tubular portion l by any suitable means according to the material employed for making the diaphragm. When the diaphragm is made of paper or cardboard hot wax is usually employed to seal the joint. In this construction the axial half-section of the diaphragm is made up of two straight lines, one at a large angle and the other at a very small angle, but in the construction shown in Figure 2 the angle at is rounded off by means of a small curve. The elongated tubular portion in either case may be more resilient than the truncated cone portion. The tubular portion I may be made of difierent material from that employed for the truncated portion 4. When the diaphragm is made of moulded material'it may be continuously curved, as shown in Figure 3. Obviously, the diaphragms may be made of any suitable material, such as paper, cardboard, fabric, metal, glass, or synthetic material. The cone-like diaphragms are preferably circular in cross-section but they may be of square, octagonal or any other form in cross-section. If the area of the tubular portion is enlarged greater power could be handled. It will be seen that the tubular portions I of the diaphragms shown take the part l' of the exponential horn shown in Figure 4 and the portions 4 take the part of the open or flared end 4 of the horn, thus the diaphragm is reduced to a convenient dimension in depth and I have found that by reducing the area of the apex portion it is this portion that loads up and gives effect to the lower frequencies. The widened-out portion reproduces the higher notes and acts as an amplifier.

Any of the above described diaphragms may be used in connection with loudspeakers. In Figure 5 I have shown the type of diaphragm illustrated in Figure 1 attached to a loudspeaker unit 6 and connected to a baille 1 by suspension cords or the like 8, preferably three or four suspension cords being provided. These cords or connecting members 8 may be of any suitable material, they may be resilient or resiliently mounted, and may be disposed as shown by full and/or dotted lines. I have found that the best position for the baflle 1 is slightly behind the flared portion or rim of the diaphragm.

It will be understood that this cone acts as a diaphragm and is connected directly to the moving iron or the like of the speaker by any convenient means. Obviously it may be connected in any convenient manner to a moving coil type of unit and its outer diameter may be suspended or connected to a baflle by any of the usual means.

If desired, the diaphragm may take the shape of an ordinary exponential horn or the ordinary horn shown in Figure 6. In this case the greater portion of the length is of small diameter and resembles an elongated slightly conical tube.

Any of the above described diaphragms may be used in connection with gramophones. In Figure 7 the apex 9 of the diaphragm consisting of the cones l and 4, is fitted with means for the reception of a gramophone needle. Such means may comprise a metal block or the like Ill having an aperture II for the reception of the needle, not shown, and an adjusting and tightening screw [2. If desired, means may be provided to adjust the position of the needle to vary the tone. Any suitable means may be provided for suspending the diaphragm in such a manner that it will vibrate throughout length.

In Figures 8 and 9 the outer end 4 of the diaphagm is suspended from a movable arm l3 attached to the gramophone body I4. The needle holder in may be also mounted to this arm ill or to a side extension thereof in any convenient manner.

In a modified construction the flared opening 4 of any of the above described diaphragms may be arranged adjacent to a tone arm l5 and 8.

horn of any usual or convenient size. As shown in Figure 10, it will be seen that the cone consisting of the two parts I and 4 acts as a diaphragmand is connected directly to the needle carrier l0 and that this diaphragm is disposed behind the usual horn IS. The flared end l6 of the diaphragm may be disposed between rubber rings or the like l1 fitted to the inner end of the horn similar to an ordinary sound box In this case the larger portion of the diaphragm would have a diameter of say two inches and the flared end of the diaphragm may be formed with lugs adapted to be disposed between the rubber rings H, the arcuate spaces between the lugs being filled with light baiile fabric, such as silk, cotton, or thin leather.

The improved diaphragm may be fitted to a horn in such a manner as to occupy as small a space as possible. This horn may be bent to any suitable shape and may be of any shape in cross-section, such as round or square. The diaphragm may be fitted to an ordinary tone arm of a gramophone which tone arm communicates with a horn, in the usual manner, disposed in the casing of a gramophone.

In a further modification as shown in Figure 1, the tubular extension or the part It! having a small apex may be arranged within the conical part 4, the apex of the cone 4 in this case being connected with a loudspeaker unit or the like 6.

Although I have described diaphragms particularly suitable for electrical or gramophone reproduction it will be obvious that such diaphragms may be connected to other impulse devices, such as to strings of instruments or used as a bell.

Such forms of diaphragms as shown in Figures 1, 2 or 3, may be of small dimensions and fitted within a telephone receiver. In this case the apex of the cone is connected to a reed or moving iron acted upon by the magnets which would be elongated to fit into existing ear-pieces.

It will be seen from the above that the invention consists in providing a diaphragm with a very small apical angle and it does not refer to a small angle that may be formed close to the apex of one of a series of steps moulded in the surface of a cone whose general or contour angle will still be large, such as 100. Also, it does not refer to a terminating angle large or small that might be formed right at the apex of a cone as a seating for a nut, washer or connector.

What I claim is:-

1. A diaphragm of conical formation, capable of vibrating freely over its full area in sympathy with the impulses transmitted axially at substantially the center of the cone, the diaphragm including a conical portion having an apical angle of less than 30 and an axial depth substantially greater than the maximum dimension across the mouth.

.2. A diaphragm o1 conical formation capable of vibrating freely over its whole area in sympathy with the impulses transmitted axially at substantially the center of the cone, the diaphragm including a conical portion, the apical part of which is deep in comparison with the maximum dimension across the mouth.

3. A diaphragm of conical formation capable of impulse-responsive vibration over its whole area, including a conical portion of substantially tubular formation and an axial depth substantially greater than the diameter of the mouth.

4. A diaphragm of conical formation capable of impulse-responsive vibration over its whole area, including a conical portion having an apical angle of less than 30 and an axial depth substantially greater than the maximum dimension across the mouth, the inner end of the portion having the small apical angle being designed for responsive connection to a gramophone needle.

5. A diaphragm of conical formation capable of impulse-responsive vibration over its whole area, including a conical portion having an apical angle of less than 30 and an axial depth substantially greater than the maximum dimension across the mouth, the inner end of the portion having the small apical angle being designed for impulse-responsive connection to a loudspeaker unit.

6. An acoustic cone diaphragm capable of impulse-responsive vibration over its whole area including a portion having an apical angle of less than 30 and an axial depth greater than the diameter across its mouth, and a truncated conical portion of larger angle provided at the mouth of said apical portion.

7. An acoustic cone diaphragm capable of impulse-responsive vibration over its whole area, including a portion having an apical angle of less than 30 and an axial depth greater than the diameter across its mouth, and a truncated conical portion of larger angle provided at the mouth of said apical portion, the outer rim of the truncated conical portion being designed for connection with a baflle disposed slightly behind the rim.

8. An acoustic cone diaphragm capable of impulse-responsive vibration over its whole area, comprising a tubular portion having an axial depth greater than its diameter, and a truncated conical portion of larger angle provided at the mouth of said tubular portion.

9. An acoustic cone diaphragm capable of impulse-responsive vibration over its whole area, comprising a portion having an apical angle or less than 30 mounted within a conical portion of the larger angle.

FRANK HARRISON. 

